Hydrogen is desirable as a source of energy because it reacts cleanly with air producing water as a by-product. In order to enhance the desirability of hydrogen as a fuel source, particularly for mobile applications, it is desirable to increase the available energy content per unit volume of storage. Presently, this is done by conventional means such as storage under high pressure, at thousands of pounds per square inch, cooling to a liquid state, or absorbing hydrogen into a solid such as a metal hydride. Pressurization and liquification require relatively expensive processing and storage equipment.
Storing hydrogen in a solid material provides relatively high volumetric hydrogen density and a compact storage medium. Hydrogen stored in a solid is desirable since it can be released or desorbed under appropriate temperature and pressure conditions, thereby providing a controllable source of hydrogen.
Presently, it is desirable to maximize the hydrogen storage capacity or content released from the material, while minimizing the weight of the material to improve the gravimetric capacity. Further, many current materials only absorb or desorb hydrogen at very high temperatures and pressures, which results in costly and industrially impractical energy requirements. Additionally, many of these systems are not readily reversible, in that they cannot absorb hydrogen upon contact at reasonable temperature and pressure conditions, and as such do not cyclically absorb and desorb hydrogen in an industrially practicable manner. Thus, it is desirable to find a hydrogen storage material that generates (releases) and reabsorbs hydrogen at relatively low temperatures and pressures, and further has a high gravimetric hydrogen storage density. There is an ever growing demand for a reversible high hydrogen content hydrogen storage material that minimizes required energy input.